The present invention relates to a measuring device having an automatic leveling function.
In a measuring device which performs a distance measurement and an angle measurement, a measuring device main body needs to be horizontally installed. The measuring device includes a leveling device, and further includes a tilt angle measuring device for detecting a leveling state and a horizontality.
As a tilt angle measuring device, there is a tilt angle measuring device which uses the fact that a free liquid surface maintains a horizontality, and as the tilt angle measuring device which uses the free liquid surface, there is, e.g., a tilt sensor.
As regards the tilt sensor, when a device main body, on which the tilt sensor is provided, tilts, the free liquid surface relatively tilts with respect to the device main body.
By entering of a detection light on the free liquid surface, receiving the detection light as reflected on the free liquid surface and detecting a change of a light receiving position caused by the tilt of the liquid surface, a tilt angle of the liquid surface, i.e., the tilt of the device main body can be detected.
In a case where the free liquid surface is used, a followability or a stability of the free liquid surface with respect to a change in tilt of the tilt angle measuring device is affected by a viscosity of a liquid forming the free liquid surface.
That is to say, when a viscosity of a liquid is lower, a followability gets better, but a stability is decreased and becomes susceptible to a vibration or the like. Contrarily, when the viscosity of the liquid is higher, the followability is lower, and a tilt angle detection takes time, but the stability gets better.
Usually, in a measuring instrument, since a measurement accuracy is important, a tilt sensor with a higher viscosity of a liquid and a higher stability is adopted.
In a case where the viscosity of the liquid is higher, there is a problem that the followability of the liquid is poor and the leveling requires time.